The present invention relates generally to medical electrical leads, and, more particularly, to implantable medical leads for connecting a stimulation device such as a pacemaker or defibrillator to a heart.
Present day cardiac stimulation leads are required to not only have multiple conductors to serve multiple electrodes but they also need to have various sections be of different stiffness or flexibility. However, current lead bodies employ one extruded tubing with one or more lumen to carry conductors. They do not meet the current requirements for the new types of leads such as combinations of pacing/defibrillation and combination left and right side leads.
Typically, implantable medical leads carry multiple conductors and, as such, have previously either employed lead bodies formed of extruded, multiple lumen tubing or have employed a coaxial structure, in which single lumen tubes are mounted coaxially around one another to define multiple lumens in which conductors may be located.
One instance of a recent improved design of lead body is disclosed in U.S. Pat. No. 5,935,159 to Cross, Jr. et al. In this instance, the lead body is formed of separate parts including an extruded core or strut member which is provided with longitudinally extending grooves in which conductors may be located and an outer tubing member, surrounding the core. The outer tubing and the core together define multiple lumens in which conductors may be located. This construction was said to simplify the manufacture of a lead, as it allows the conductor simply to be laid in the elongated grooves of the core, rather than requiring that they be pushed or pulled along the lengths of preformed lumens. In some embodiments of that earlier invention, the core is provided with a central, reinforcing strand, extending along the length of the lead, providing for structural integrity and high tensile strength. The core may be manufactured as a single extrusion, extending the entire length of the lead, or may take the form of sequentially aligned multiple extrusions of differing materials to provide for differential flexibility along the length of the lead.
It was in light of the foregoing that the present invention was conceived and has now been reduced to practice.
An implantable endocardial lead includes a first elongated tubular component of flexible resilient material with a first face and a first longitudinally extending channel forming a partial lumen in the first face, a similar second elongated tubular component with a second face opposite the first face and a second longitudinally extending channel forming a partial lumen in the second face, the first and second tubular components being integrated by contiguously uniting the first and second faces with the first and second partial lumina being in mutually overlying relationship forming a full lumen within the elongated lead body. Elastic rings received in longitudinally spaced annular grooves provided in the outer peripheral surface of the elongated lead body bias together the first and second elongated tubular components. An elongated electrical conductor is received in the full lumen and an overlying sheath is in contiguous engagement with the peripheral outer surface.
The invention presented in this disclosure is an improvement over the Cross, Jr. et al. lead design discussed above. The present invention allows two or more extrusions to be fitted together axially, after the conductors are placed in their respective lumina. Properties of stiffness or flexibility along the catheter/lead length can be altered in one of two ways:
1) lengths of such extrusions with different properties, for example shore hardness, can be added together to form an inner construction for a lead; and
2) the distance between the annular grooves can be altered; those regions at which the elastic rings engaged in the annular grooves are placed further apart will have greater flexibility than those regions at which the elastic rings engaged in the annular grooves are placed nearer together.
Subsequently, as above noted, an outer extruded tubing or a sheath can be fitted over the inner body construction to constitute a lead body.
According to the invention, then, assembly of the lead body could entail, but need not necessarily be restricted to the following operation steps:
1. The conductors, that is coated or uncoated cable or coil are placed into the appropriate lumen or lumina of half-tubing, made of a suitable medical grade implantable material, for example silicone, polyurethane, or a suitable combination thereof. The tubing may have a single lumen or a plurality of lumina at given cross-sections along the length of the catheter or lead.
2. The other half of the tubing is placed over the first half while ensuring that the grooves of the two halves of the tubing are aligned. A ring made of a suitable elastic material may be slid over the insulation material and into the grooves. Alternatively, a medical grade adhesive or other suitable bonding agent could be used to bond the two halves of the tubing together.
3. Additionally, an outer sheath, made of a suitable material such as silicone, polyurethane, or a combination thereof may be slid over the lead body sub-assembly to hold all its components in place. Numerous cross sections of a catheter or lead body can employ this method of assembly.
By increasing or decreasing the number of grooves and subsequently the number of rings a lead body can hold, the flexibility for different sections along the length of the catheter or lead body can be altered as desired.
A primary feature, then, of the present invention is the provision of an improved technique for manufacturing medical electrical leads, especially implantable medical leads for connecting a stimulation device such as a pacemaker or defibrillator to a heart.
Another feature of the present invention is the provision of such a technique which facilitates the process of manufacture of an implantable medical catheter or lead.
Yet another feature of the present invention is the provision of such a technique according to which flexibility or stiffness can be desirably varied along the length of a catheter or lead body.
Still a further feature of the present invention is the provision of such a technique according to which an elongated lead body of flexible resilient material includes a first elongated tubular component having a first face and a first longitudinally extending channel forming a partial lumen in the first face, a second elongated tubular component having a second face opposite the first face and a second longitudinally extending channel forming a partial lumen in the second face, the first and second elongated tubular components being integrated by contiguously uniting the first and second faces with the first and second partial lumina being in overlying relationship resulting in a full lumen within the elongated lead body.
Yet a further feature of the present invention is the provision of such a technique according to which the elongated lead body has a peripheral outer surface with a pair of longitudinally spaced annular grooves therein and an elastic ring is received in each of the annular grooves for biasing together the first and second faces of the first and second elongated tubular components.
Still another feature of the present invention is the provision of such a technique according to which an elongated electrical conductor is received in the full lumen.
Yet another feature of the present invention is the provision of such a technique according to which the first and second faces are bonded together by adhesive.
Still a further feature of the present invention is the provision of such a technique according to which the elongated lead body has a peripheral outer surface and includes an overlying sheath in contiguous engagement with the peripheral outer surface.
Yet a further feature of the present invention is the provision of such a technique according to which an elongated lead body of flexible resilient material includes first and second elongated tubular components having mutually opposed faces with at least one of the tubular components having a longitudinally extending lumen, the tubular components being integrated by contiguously uniting the first and second faces.
Other and further features, advantages, and benefits of the invention will become apparent in the following description taken in conjunction with the following drawings. It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory but are not to be restrictive of the invention. The accompanying drawings which are incorporated in and constitute a part of this invention, illustrate one of the embodiments of the invention, and together with the description, serve to explain the principles of the invention in general terms. Like numerals refer to like parts throughout the disclosure.